The present invention relates to catheters and leads generally, and more particularly to implantable electrode leads for connection to an implantable pulse generator or monitoring device.
Implantable leads are used in conjunction with implantable stimulators and monitoring devices to carry electrical signals to the devices and stimulus pulses from the devices to body tissue. Rather than being manufactured as a single device, the electrode leads are typically manufactured as separate devices, requiring that they be interconnected with the implantable medical device. Typically, this interconnection has been by means of a connector assembly located on the proximal end of the electrode lead which is inserted into a connector bore located in the medical device.
At present, electrical connectors for use in conjunction with cardiac pacemakers and their associated leads generally correspond to the IS-1 connector standard. As an example of a lead connector meeting the IS-1 connector standard can be seen in U.S. Pat. No. 4,951,687 issued to Ufford et al. and incorporated by reference herein in its entirety. Connector assemblies for use in conjunction with implantable defibrillators, and in particular for use in conjunction with high energy cardioversion and defibrillation electrodes may correspond to the "DF-1" configuration, presently employed on Cardioverter/defibrillator leads as manufactured by Medtronic, Inc. In conjunction with connectors having the above configurations, sealing rings are provided on the connector assemblies which serve to seal the connector bores from fluid entry and to seal the connector bores between the electrical connectors coupled to the electrodes located on the lead. Insertion of the leads into the connector bores thus creates a certain amount of frictional resistance, in turn requiring that the proximal portion of the lead be configured in such a fashion that it is possible for the physician to push the lead into the connector socket.
Traditionally, cardiac pacing leads have employed conductors taking the form of monofilar or multifilar metal coils, which by their nature substantially stiffen the portion of the lead through which they pass. However, more recently designed implantable pacing and defibrillation leads may employ cabled conductors of the sort described in U.S. Pat. No. 5,246,014 issued to Williams et al. and U.S. Pat. No. 5,584,873 issued to Shoberg et al., both incorporated by reference in their entireties. Such conductors do not significantly add to the stiffness of the lead body, rendering the lead body carrying these conductors relatively more flexible than a corresponding lead body with the same number of coiled conductors. This in turn may render the proximal end of the lead more difficult to insert into the associated connector bore in the implantable stimulator or monitor with which the lead is intended to be used.
Prior leads employing cabled conductors have employed two basic mechanisms in order to assist the physician in inserting the proximal end of the lead into the connector bore of the associated device. The first mechanism is a provision of a coil or tube, mounted within the lead body and extending distally from the proximal end of the lead body which provides the proximal end of the lead body with increased column strength and some increase in rigidity to assist insertion of the connector assembly on the lead into the connector bore of the associated device. The second mechanism has then the provision of a tubular stress relief sleeve, mounted over a proximal portion of the lead body, which the physician may grasp when inserting the lead.
A second set of problems associated with the construction of the proximal portion of the lead body is that these portions of the lead body typically lie adjacent the implantable stimulator or monitor, in the subcutaneous pocket in which the device is implanted. In such case, the proximal portions of the lead body have the potential of repeatedly rubbing against the housing of the implanted device, carrying with it the potential problem of abrasion of the lead body and possible exposure of one or more of the conductors therein. This problem becomes more significant in the case of devices which are provided with porous or roughened surfaces, for example, by bead blasting as disclosed in U.S. Pat. No. 5,673,473 issued to Johnson et al, also incorporated herein by reference in its entirety.